## Fundamentals of Electrical Engineering

Voltage: $JC^{-1}$ Current: $Cs^{-1}$ Resistance: $JsC^{-2}$
Voltage is defined as the amount of electric potential energy required to transport one unit of charge from one point to another in a closed circuit. Since the SI unit for energy is the Joule ($J$) and that for charge is the Coulomb ($C$), the SI unit for voltage is Joules per Coulomb ($JC^{-1}$). Current is defined as the amount of charge passing through a point in a closed circuit per unit time. Since the SI unit for charge is the Coulomb ($C$) and that for time is the second ($s$), the SI unit for current is Coulombs per second ($Cs^{-1}$). Resistance is defined as the ratio of voltage applied to a point in a circuit to the amount of current flowing through it. Having obtained the SI units for both voltage ($JC^{-1}$) and current ($Cs^{-1}$), by Ohm's Law of $V=IR\Rightarrow{R}=\frac{V}{I}$, the SI unit for resistance is Joule seconds per Coulomb squared ($JsC^{-2}$). This is commonly known as the ohm ( $\Omega$).